In the past, computer displays have generally been connected directly to the computers that are driving them by means of a ‘monitor cable’. This direct electrical connection made it very clear which machine was driving which display. Increasingly, however, the electrical limitations of the cable, which mean that it cannot be more than a few meters long, and the lack of flexibility in this dedicated one-to-one mapping, have prompted the creation of displays and display adaptors which can be connected to a general-purpose data network such as Ethernet, USB, IEEE 1394, powerline, 802.11 or UWB wireless. Such systems allow a display to be placed at a much greater distance from the machine driving it, and allow one machine to drive many displays, or one display to be updated by many different machines. Henceforth in this document, we will use the term ‘display’ or ‘screen’ with the assumption that we are referring to display devices to which graphical information may be sent over the network.